Language disabilities in three twin pairs and their relatives.

Three pairs of monozygotic twins were ascertained during a general survey of language disabilities conducted among schoolchildren of Porto Alegre, Brazil. Two of them were concordant for dysgraphia, dysorthographia, dyslexia, and speech defects, while the other was concordant for dysorthographia and dyslexia, but discordant for dysgraphia. Two of the mothers and two sibs also presented language problems, but of a type that was not completely similar to those of the twins. Concomitant neurological and psychological studies, as well as the family histories, helped to understand the similarities and dissimilarities observed.